I was wondering if you could put the Pressurized Cargo Module (PCM) for Cygnus in the Dragon Trunk?

The PCM for Cygnus has a diameter of 3.07m and a height that looks to be about 2.4m. The dry mass is 1,500kg including the service module I think, so maybe just 750kg for the PCM?

Dragon has a diameter of 3.7m and CRS-8 is carrying BEAM in the trunk and BEAM has a 3.2m diameter (although this likely is less for transport) and 4m height and is 1,360kg.

It seems like it would fit to me. Thoughts?

No.

A. the Dragon can not maneuver with itb. The PCM is not made to be pulled into orbitc. Trunk does not the structural capabilityd. No performance to carry it

All that plus:e. Trunk has radiators and solar panels. Cygnus has those on the service module.f. would still need two adapters since Trunk is also the adapter to the F9 upper stage. And the smaller diameter of the Cygnus PCM would need to be attached to the wider Dragon base. And avoid damaging the heat shield at that.g. If you look at the integrated Dragon, it has an attachment on the side from the Trunk to the capsule. It's usually called the Claw, but it routes power, heat rejection and data. You'd have to route that along the PCM.h. It's easier to develop a PCM for Dragon than start from the Cygnus PCM. It's an idea I've proposed multiple times for CRS2.

Month ago or so (I do not remember exactly who, I just remember post) someone fumed at even mentioning possibility that Orbital would buy launch from SpaceX. After all, they are cutthroat competition, not in milion years or something.

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Month ago or so (I do not remember exactly who, I just remember post) someone fumed at even mentioning possibility that Orbital would buy launch from SpaceX. After all, they are cutthroat competition, not in milion years or something.

Yes, there is one who would insist that no choice is preferable to Atlas V.

Month ago or so (I do not remember exactly who, I just remember post) someone fumed at even mentioning possibility that Orbital would buy launch from SpaceX. After all, they are cutthroat competition, not in milion years or something.

Well, they are no more "folks" but only "someone", that doesn't mean anything.Orbital is a private old space company with some new space lipstick, they are mostly interested in $$$. So if they can make more $$$ by launching on Falcon 9 they will.

Not saying it would fit in the trunk or anything like that, but ISTM F9E has quite a lot of performance in reserve when it lifts Dragon.

Cheers, Martin

The limitation would not be the payload capacity of Falcon 9 it would be the payload capacity of Dragon. According to wikipedia Dragon has a maximum payload of 3310kg. The dry mass of Cygnus would be included in this total mass.

Not saying it would fit in the trunk or anything like that, but ISTM F9E has quite a lot of performance in reserve when it lifts Dragon.

Cheers, Martin

The limitation would not be the payload capacity of Falcon 9 it would be the payload capacity of Dragon. According to wikipedia Dragon has a maximum payload of 3310kg. The dry mass of Cygnus would be included in this total mass.

Edited for clarity.

That appears to be a Dragon limitation, not an F9 one. I suspect the limitation is in total impulse and control authority of Dragon's thrusters.

Just a reminder, Dragon and Cygnus can't be linked. As you point out, Dragon can't possibly cope with the extra mass, and neither were designed to cope with being combined, anyway.

Assuming no payload in Dragon's trunk, any part of that 3310kg that won't fit in the pressurised volume becomes available to be part of Cygnus' mass.

If Cygnus launches underneath Dragon, it would be a completely independent secondary payload, just like that poor failed Orbcomm sat, or a CubeSat.

Given competition for the CBM, I suspect one of the pair would have to loiter while the other docks, is unloaded, reloaded and departs.

Dragon demonstrated some loiter capability on COTS 2/3, when it had to loiter after the "2" mission, before getting go to undertake the "3" mission. I believe Cygnus is quite capable of the same, if it comes to that.

Seems that this tread is heading in the wrong direction. Sure, SpaceX might be launching Cygnus on a Falcon 9 but, this will be like any other independent CRS launch. They'll just put a fairing shroud around Cygnus and off she goes to put it simply. Of course, there are a lot of different elements to the launch but, it seems completely doable otherwise Orbital and SpaceX would not even entertain it.

(1)The standard sized Cyngus probably also can fit on Stratolaunch. OSC is developing the rocket so it would make sense to go ahead and design a payload interface for their own vehicles.

Not going to happen.

Can you please say why not? Is (1) wrong or lack of performance or lack of incentives or short time scales or what?

The timescale is just too far in the future.Looking at how long White Knight took to develop and fly for VG, before you put a Cygnus on Stratolaunch vehicle it faces a similar test regime. Plus, the future is quite uncertain for the ISS (as per other threads).

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Even if Dragon is at its max mass, then 2,500 kg of cargo in Cygnus would only bring the total mass to orbit up to 10t. If we're assuming 13t to std LEO, then I'd think that 10t would be possible to ISS inclination.

Not included in this mass is an adapter required to accommodate Cygnus under Dragon - it looks way too big to fit into the trunk.

However, I'm assuming Dragon's mass will be well under 6,000 kg as I wouldn't imagine it would carry any trunk cargo, so it appears to me the total mass to orbit would be well under 10t.

The biggest issue (and I think makes it completely impossible in the timeframe), is having to develop the adapter / trunk extension to physically accommodate Cygnus. This would also, of course change the relationship of Dragon to the TEL (total height of the stack).

Thanks to Jim and everyone who replied to my post. I think my problem is lack of solid information on the hight and mass of the PCM of cygnus and the dimensions of what will fit in the dragon trunk.

The sources I can find indicate cygnus is 3.66m high and 1,500kg for the whole thing. Does anyone know how much just for the PCM? Assuming both dry, which would have more mass, the PCM or SM?

If dragon can carry 3,300kg total, and carries 1,500kg of its own pressurized cargo, that leave 1,800kg for the trunk. If the PCM alone is 800kg that leaves 1,000kg for PCM cargo. I don't know the mass of the PCM, but it looks like mass is not a problem. As I say I would be very interested in better information.

In term of height I estimated PCM at 2.4m, because the extended cygnus adds 1 segment and 1.2m, the normal cyguns is made up of 2 segments.

Beam is going in the trunk for CRS-8, and it is 4m tall, so the PCM should be smaller. So is the problem diameter? Beam is supposed to be 3.2m, and Cygnus is 3.07m, but maybe that is the inflated diameter of beam, not what travels in the trunk.

I was thinking the Canada arm could just pull PCM out of the trunk after berthing.

Anyways, I'm happy to be wrong, but I don't understand what the wrong assumptions are that I have made. If anyone can provide more details on what is wrong with my calculations I would appreciate it.

As an aside, Dragon is volume constrained, maybe Spacex could add their own PCM to the trunk for the next contract. It would have to be disposable, which isn't there style, but it could significantly add to their pressurized volume.